Stem Cells Basics > The Science of Stem Cells

The Science of Stem Cells

The defining characteristics of stem cells are that they are capable of self-renewal, meaning they can divide numerous times and maintain their undifferentiated state, and they are multipotent, meaning they have the potential to change into or differentiate into several different cell types. Scientists and doctors are optimistic about the growing role of stem cells to treat serious diseases.

There are two broad types of stem cells:

Embryonic stem cells have the ability to create all cell types in our bodies. They have tremendous potential, but have not yielded any proven treatments and have been found to form tumours when implanted in animals. Embryonic stem cells are usually created by collecting and culturing cells from an embryo, often resulting in the embryo's destruction. The ethical and technical issues surrounding embryonic stem cells present large hurdles for successful medical applications in the near future.

Adult stem cells are multipotent, which can form more limited cell types than embryonic stem cells. Although adult stem cells typically can only create fewer tissue types, they are easier to control in research and clinical applications. Additionally since adult stem cells can be harvested from and used by the same patient, both immunogenic rejection and ethical controversy can be averted. As a result, adult stem cells are currently being used to treat dozens of diseases, and the number of applications for adult stem cells being researched, used in clinical trials, or used in clinical practice continues to grow.

There are two basic sub-types of adult stem cells:

Hematopoeitic stem cells form blood cells and are typically found in bone marrow or umbilical cord blood.

Mesenchymal stem cells form connective tissues such as bone, tendons, muscles, fat, and nerves as well as liver and pancreatic cells. Mesenchymal stem cells are typically found in bone marrow or the dental pulp in teeth.

Milestones in Adult Stem Cell History

The use of adult stem cells is not new – bone marrow stem cells were used for treatment of leukemia in the 1950s, even before we knew that stem cells were responsible for the clinical benefits. Since then, bone marrow stem cells have been used for treatment of multiple clinical conditions, and other sources of stem cells have been discovered, and other therapies developed.

Umbilical cord blood stem cells were first identified in the 1980s and have since been used for a variety of treatments. Because of this potential, cord blood banking was begun in the early 1990s, so parents can save these stem cells for possible future applications.

And since the discovery of dental stem cells in 2000…
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